The Gift of Introversion

people are sometimes hard for non-native English-speakers to understand except in a
literal sense.
Eysenck's Theory
Hans Eysenck described extraversion-introversion as the degree to which a person is
outgoing and interactive with other people. These behavioral differences are presumed
to be the result of underlying differences in brain physiology. Eysenck combined cortical
inhibition and excitation with the ascending reticular activation system (ARAS), a
pathway located in the brainstem. Extraverts seek excitement and social activity in an
effort to heighten their arousal level, whereas introverts tend to avoid social situations in
an effort to keep such arousal to a minimum. Eysenck designated extraversion as one
of three major traits in his P-E-N model of personality, which also
includes psychoticism and neuroticism.
Eysenck originally suggested that extraversion was a combination of two major
tendencies, impulsiveness and sociability. He later added several other more specific
traits, namely liveliness, activity level, and excitability. These traits are further linked in
his personality hierarchy to even more specific habitual responses, such as partying on
the weekend.
Eysenck compared this trait to the four temperaments of ancient medicine, with choleric
and sanguine temperaments equating to extraversion, and melancholic and phlegmatic
temperaments equating to introversion.
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